Search

This work is motivated by the fact that the reliability of electrical connectors influenced by their mechanical behavior and fatigue life directly affects the working performance of the whole equipment system. In this paper, theoretical analyses of insertion force, maximum stress, and fatigue life in an aviation electrical connector are presented and the corresponding mathematical models are firstly derived. Then, to numerically investigate its mechanical behavior and fatigue life, a simplified 3D FE model is developed by using ABAQUS and FE‐SAFE software and verified by experiments and theoretical analysis. Finally, the distribution and evolution characteristics of contact forces, stress and fatigue life considering the influences of reed thickness and slot width are quantitatively analyzed in details. The results indicate that the insertion force first increases and then stabilizes at the level of 0.16 N as the pin head is fully inserted into the jack, which shows an opposite to the evolution of extraction force. Moreover, the maximum value of stress and the minimum value of fatigue life are all located at the root of the jack reed. Besides, unlike the small effect of slot width, the Fimax and σmax values obviously increase and the Nf value decreases with the increment of reed thickness. [ABSTRACT FROM AUTHOR]

To develop biodegradable, sustainable, and environment-friendly functional food-packaging materials, gelatin/zein/glucose nanofibers were fabricated through air-assisted electrospinning and then crosslinked by the Maillard reaction under mild conditions (60 °C and 50% relative humidity) in this study. Compared to traditional electrospinning, air-assisted electrospinning increased the yield of nanofibers by 10 times, and the average diameter from 263 nm to 664 nm, while the airflow facilitated uniform and smooth nanofiber formation. During the Maillard reaction in 0–5 days, the gelatin/zein/glucose showed no morphology change. Fourier transform infrared spectra analysis indicated that gelatin interacted with zein through hydrogen bonding and the occurrence of the Maillard reaction among the protein and glucose molecules. After four days of Maillard reaction, the nanofibers presented higher thermal stability, the most hydrophobic surface (water contact angle: 133.6°), and stiffer network structure (elastic modulus of 38.63 MPa, tensile strength of 0.85 MPa). Overall, Maillard-reaction-crosslinked gelatin/zein/glucose nanofibers showed favorable physical properties, which suggests their potential for application in food-active packaging. [ABSTRACT FROM AUTHOR]

Objectives: The aim of the present work was to comparatively investigate the generation and characteristics of fretting and sliding wear debris produced by CuNiAl against 42CrMo4. Methods: Tribological tests were conducted employing a self-developed tribometer. Most experimental conditions were set the same except for the amplitudes and number of cycles. Morphological, chemical, microstructural and dimensional features of the worn area and debris were investigated using optical microscope (OM), X-ray diffraction (XRD), scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS) and a laser particle sizer. Outcomes: Not only wear scar profiles but also the wear debris color, distribution and generated amount under fretting and sliding wear modes were quite different, which can be attributed to the significant difference in wear mechanisms. Particle size analysis indicates that the fretting debris has a smaller size distribution range; the biggest detected fretting and sliding wear debris sizes were 141 μm and 355 μm, respectively. Both fretting and sliding debris are mainly composed of copper and its oxides, but the former shows a higher oxidation degree. [ABSTRACT FROM AUTHOR]

BACKGROUND: In recent years, there has been considerable interest in the use of biopolymer electrospun nanofibers for various food applications due to the biocompatibility, biodegradability, and high loading capacity. Herein, we fabricated and characterized novel hybrid electrospun fibers from dextran (50%, w/v) and zein (0–30%, w/v) solutions, and the effects of various zein concentrations on the properties of the hybrid electrospun fibers were investigated. RESULTS: When zein was added at low concentrations (5% and 10%), dextran and zein showed poor miscibility, as reflected by significantly decreased viscosity of the solutions, and the poor mechanical properties of the derived fiber membranes. When zein was added at medium concentrations (15–25%), hydrogen bonds were formed between dextran and zein molecules, as indicated by the red shift of Fourier‐transform infrared bands and β‐sheet to α‐helix structural transformations. The fiber membranes electrospun from a solution with 25% zein showed the most hydrophobic surface, with a water contact angle of 116.9°. The homogenous dispersion of dextran and zein resulted in improved mechanical properties for fibers electrospun from a solution with 30% zein. Curcumin encapsulating dextran/zein electrospun fibers exhibited effective radical scavenging activity and ferric reducing power, along with the desired controlled release behavior for curcumin delivery. CONCLUSION: Food grade dextran/zein hybrid electrospun fibers demonstrated tunable properties, and appear to be promising as delivery systems for bioactive and edible antimicrobial food packaging. © 2021 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

This work is motivated by the frequent occurrence of macro- and microdefects within forged Ti-6Al-4V turbine blades due to the severely nonuniform strain and temperature distributions. To overcome the problem of nonuniformity during the blade forging operation, firstly, a 2D coupled thermo-mechanical finite element approach using the strain-compensated Arrhenius-type constitutive model is employed to simulate the real movements and processing conditions, and its reliability is verified experimentally. Secondly, two evaluation indexes, standard deviation of equivalent plastic strain and standard deviation of temperature, are proposed to evaluate the uniformity characteristics within the forged blade, and the effects of four process parameters including the forging velocity, friction factor, initial workpiece temperature and dwell time on the uniformity of strain and temperature distributions are carefully studied. Finally, the numerically optimized combination of process parameters is validated by the application in a practical process. The parametric study reveals that a reasonable combination of process parameters considering the flow resistance, flow localization and the effects of deformation and friction heating is crucial for the titanium alloy blade forging with uniformity. This work can provide a significant guidance for the design and optimization of blade forging processes. [ABSTRACT FROM AUTHOR]

Friction conditions significantly impact the temperature and phases of titanium forged parts, further directly affecting the microstructures and mechanical properties of final parts. In this paper, a 2D simplified finite element (FE) model combined with phase transition equations is developed to simulate a Ti-6Al-4V drum forging procedure. Then, friction effects on the temperature and phases of the forged drum are numerically analyzed and verified by experiments. The simulated results indicate that a reasonable range of friction factor is needed to obtain a relatively homogenous temperature distribution within the forged drum. Moreover, unlike its small influence on the α + β phase, improving friction obviously decreases the general levels of temperature and β phase and increases the homogeneities of α and β phases within the forged drum, which are associated with cooling rates and the heating effects of friction and deformation. [ABSTRACT FROM AUTHOR]

[Display omitted] • New strategy for the synthesis of α -alkylated ketones based on hydrogen autotranser process. • Primary alkenyl alcohols were utilized as hydrogen sources and alkylating agents. • Functional groups in bpy ligand are crucial for transfer hydrogenation/hydrogen autotransfer process. • The catalytic system was applied to the synthesis of a biologically active compound. A new strategy for the synthesis of α -alkylated ketones from secondary alcohols and primary alkenyl alcohols via a tandem transfer hydrogenation/hydrogen autotransfer process was proposed and successfully accomplished. Mechanistic experiments supported that functional groups in bpy ligand are crucial for the transfer hydrogenation and hydrogen autotransfer process. Furthermore, the utilization of the present catalytic system for the gram-scale synthesis of a biologically active compound was presented. [ABSTRACT FROM AUTHOR]

An oxidized mesoporous carbon (OMC) with fluffy structure was fabricated from the mixture of petroleum asphalt and aluminum isopropoxide, and its structures were characterized by FESEM, TEM, BET, TG, XPS and FT-IR. In addition, bath absorption experiments for malachite green (MG) and lead ion (Pb 2+ ) were carried out to explore the effects of pH, initial concentration, contact time and temperature on its absorption process. Results show that the OMC prepared has a fluffy ultrathin-wall structure with narrow pore size distribution and rich oxygen-containing groups. It exhibits excellent absorption performance for the removal of MG as well as Pb 2+ , as indicated by that its maximum adsorption capacity is 963.1 mg g −1 for MG and 198.6 mg g −1 for Pb 2+ . The absorption experimental data are all fitted well with pseudo-second-order model and Frendlich isotherm, respectively. More importantly, the OMC still maintains relatively high adsorption capacity after five cycles. [ABSTRACT FROM AUTHOR]

This paper investigates torsional-fretting wear properties of 7075 aluminum alloys under lubricated and dry conditions. Fretting wear experiments are conducted under the flat-on-flat contact configuration, followed by the friction torque, dissipated energy and wear volume analyses. The worn area morphology, wear mechanism and tribo-chemical behavior are examined by the optical microscopy, scanning electron microscopy and X-ray photoelectron spectroscopy, etc. The fretting behavior is obviously affected by a collective effect of the lubricating medium, third body behavior and contact configuration. Abrasion wear by micro-cutting of debris is detected on the oil lubricated worn surfaces. The abrasion, cracks and delamination are commonly exist on the seawater lubrication and dry fretting worn surfaces. Corrosion pits and an oxidation debris layer can be observed under the former and latter test conditions, respectively. • Practical 7075 aluminum alloy applications refer to the flat-on-flat configuration. • The fretting wear properties of 7075 alloys were investigated at the flat-on-flat cotact. • Tribological behaviors were affected by the lubrication and third-body behaviors. • The corrosion effect of seawater plays an important role during the fretting process. [ABSTRACT FROM AUTHOR]

Abstract: Background: Protein kinase ataxia telangiectasia mutated (ATM) regulates the function of endothelial cells and responds quickly to endotoxin. However, the function of ATM in lipopolysaccharide (LPS)-induced blood-brain barrier (BBB) disruption remains unknown. This study aimed to investigate the role and underlying mechanism of ATM in the regulation of the BBB function in sepsis. Methods: We used LPS to induce BBB disruption in vivo and to establish an in vitro model of cerebrovascular endothelial cells. Blood-brain barrier disruption was assessed by measuring Evans blue leakage and expression of vascular permeability regulators. To investigate the role of ATM, its inhibitor AZD1390 and clinically approved doxorubicin, an anthracycline that can activate ATM, were administered as scheduled. To explore the underlying mechanism, protein kinase B (AKT) inhibitor MK-2206 was administered to block the AKT/dynamin-related protein 1 (DRP1) pathway. Results: Lipopolysaccharide challenge induced significant BBB disruption, ATM activation, and mitochondrial translocation. Inhibiting ATM with AZD1390 aggravated BBB permeability as well as the following neuroinflammation and neuronal injury, while activation of ATM by doxorubicin abrogated these defects. Further results obtained in brain microvascular endothelial cells showed that ATM inhibition reduced the phosphorylation of DRP1 at serine (S) 637, promoted excessive mitochondrial fission, and resulted in mitochondrial malfunction. By activating ATM, doxorubicin increased the protein binding between ATM and AKT and promoted the phosphorylated activation of AKT at S473, which could directly phosphorylate DRP1 at S637 to repress excessive mitochondrial fission. Consistently, the protective role of ATM was abolished by the AKT inhibitor MK-2206. Conclusions: Ataxia telangiectasia mutated protects against LPS-induced BBB disruption by regulating mitochondrial homeostasis, at least in part, through the AKT/DRP1 pathway., Competing Interests: The authors report no conflict of interest., (Copyright © 2023 The Author(s). Published by Wolters Kluwer Health, Inc. on behalf of the Shock Society.)

A new strategy for the synthesis of N ', N '-methylaliphatic acylhydrazides from acylhydrazones via transfer hydrogenation/ N -methylation with methanol as both the hydrogen source and the methylating reagent has been proposed and accomplished. In the presence of [Cp*Ir(2,2'-bpyO)(H 2 O)] (1 mol %) and Cs 2 CO 3 (0.3 equiv), a range of desired products were obtained in high yields. It was also confirmed that functional units in the bpy ligand of the catalyst are crucial for the catalytic activity of iridium complexes. The mechanistic investigation and practical application of the present catalytic system were also presented.

Rationale : Hosts defend against viral infection by sensing viral pathogen-associated molecular patterns and activating antiviral innate immunity through TBK1-IRF3 signaling. However, the underlying molecular mechanism remains unclear. Methods : SiRNAs targeting Sirt1-7 were transfected into macrophages to screen the antiviral function. Sirt5 deficient mice or macrophages were subjected to viral infection to assess in vivo and in vitro function of Sirt5 by detecting cytokines, viral replicates and survival rate. Immunoprecipitation, WesternBlot and luciferase reporter assay were used to reveal molecular mechanism. Results : In this study, we functionally screened seven Sirtuin family members, and found that Sirtuin5 (Sirt5) promotes antiviral signaling and responses. Sirt5 deficiency leads to attenuated antiviral innate immunity in vivo and in vitro upon viral infection by decreasing TBK1-IRF3 activation and type I IFN production. Sirt5 overexpression increased antiviral innate immunity. Mechanism investigation revealed that Sirt5 interacts with DDX3 and demalonylates DDX3, which is critical for TBK1-IRF3 activation. Mutation of the demalonylation lysine sites (K66, K130, and K162) of DDX3 increased ifnβ transcription. Furthermore, the acetylation on lysine 118 of DDX3 positively regulated ifnβ transcription, whereas Sirt5 could not deacetylate this site. Conclusion : Sirt5 promotes anti- RNA and DNA virus innate immune responses by increasing TBK1 signaling through demalonylating DDX3, which identifies a novel regulatory pathway of antiviral innate immune response., Competing Interests: Competing Interests: The authors have declared that no competing interest exists., (© The author(s).)